Many devices have been proposed for measurement of rain. One of the most primitive means for measuring rain is placing a tube marked with measurement increments in an outdoor area exposed to the rain. Other means include the use of sight glasses, magnetic and mechanical float level sensors (including magnetostrictive, resistive chain level sensors), pneumatic level sensors (nitrogen bubblers), microwave/radar level sensors, optical level sensors, ultrasonic or sonar level sensors, hydrostatic pressure sensors.
The tipping bucket rain gauge is another alternative to the standard rain gauge for measuring rainfall. Two specially designed buckets tip when the weight of 0.01 inches of rain falls into them. When one bucket tips, the other bucket quickly moves into place to catch the rain. Each time a bucket tips, an electronic signal is sent to a recorder. To calculate the rainfall for a certain time period, the number of marks on the recorder is multiplied by 0.01 inches. The tipping bucket rain gauge is especially good at measuring drizzle and very light rain events. If the recorder is equipped with a clock, you can determine how much rain fell during certain time periods without actually being present at the station. However, one weakness of the tipping bucket rain gauge is that it often underestimates rainfall during very heavy rain events, such as thunderstorms.
Unfortunately, the prior art conventional rain gauge devices suffered from a variety of disadvantages. Many devices suffered from low reliability, low accuracy, excessive maintenance and/or recalibration requirements, low repeatability or precision, high cost, and high failure rate mainly because the conventional rain gauge device utilized moving parts, which increased the occurrence rate of failures attributable to such parts. And, many of these conventional rain gauge devices do depend, in some fashion, upon the physical properties of the fluid such as density and temperature, and thus require recalibration and/or reconfiguration of the rain gauges in different conditions.
Additionally, the prior art level rain gauge devices are not suited for precisely measuring rainfall accumulation over time and are not well adapted to providing necessary warnings of impending floods. This is a major draw back in the prior art. Increasing urban development, subsidence of land due to consumption of ground water, and increasing severity of weather conditions are increasing the frequency and severity of flooding in many areas. The National Oceanic & Atmospheric Administration (NOAA) estimates around 5,321 flash flood deaths in the United States between from 1960 to 2006. NOAA warns that flash floods and floods are the number one weather-related killer, with around 140 deaths recorded in the United States each year. Floods on average are also responsible for $4.6 billion in damages in the each year in the United States alone.
Given the gravity of flooding problems in the United States and abroad, a need exists for accurate and reliable measurement devices capable of measuring an accumulation of rainfall that are able to warn surrounding residents and weather stations of flood conditions and thereby allow for sufficient time to evacuate low-lying areas. Accordingly, it would be desirable to have rain gauge devices that rely less on moving parts, and the density properties of fluids in order to obtain an accurate measurement heading. Importantly, a gauge that provides a simple “on” “off” signal at a measurement increment is needed. Accurate measurements of rainfall also can be used to check alternate rainfall measurements such as radar, and calibrate them, in order to predict aquifer usage for crop watering, and predict water supply shortfalls. On a small scale, a homeowner could better judge how often to water his land, noting that areas served by radio or television stations are large and their coverage area varies greatly not only in the amount of rain measured but in whether there was rain.